Rolling out a ROApp - Programming GPS and OpenStreetMap Applications with Java - page 181

Now what are RemotePlayerInfo is Technically speaking, a real object is
running on its private host, can identify, enter, and exit one server, enter
another one, etc. In addition, the object can choose to publish itself on its
host:
rmi://ROHost:port/myRealObject
This is not used in the game scenario for a simple reason: imagine one of
the chasers having a direct reference and access to a runner's API. The
chaser would skip the third party to validate and propagate game info, and
the runner could not be hidden by the application|which is vital to play
the game according to its rules. Nevertheless, you might create a team of
players, who have direct access to each other to coordinate their moves and
motion. The server wouldn't know.
Recall that the LCPlayer , being a RealObject , implements the Player
Client to realize the RemotePlayer API as required to play on the game
server. On the server side, the ServerPlayer , also being a RealObject com-
municates with the RemotePlayer during the game, while its RemoteClient
is not being used yet.
The server (developer) can use the ServerObject.RemoteClient to publish
a remote object reecting the client's behavior. Any client can look up the
remote object by its URL and frequently sample it with getGPSinfo() .
This is exactly what each LCPlayer does to get information about the other
players. The server can now focus on controlling the game, while each
client can actively retrieve the current status as needed.
On the other hand, the server can not steer this additional object, since
the server object can only propagate its client's actions; also the server does
not have access to the client implementation. In the context of LondonChase ,
the PlayerInfoClient is used to provide relevant game information via the
RemotePlayerInfo API; for example, the game role of each player.
Generally, a ROServer with the address
rmi://ROServerHost:<port>/ROAppName
can also choose to publish its ServerObject s, for example,
rmi://ROServerHost:<port>/ROAppName/ROName123
to indicate where the ROs come from, belong to, and are validated by.
The server accounts for his published clients. In LondonChase , all server (!)
players of a game are published and are looked up by its LCPlayer s|
including their own reflection! This way the player can easily compare the
behavior propagated by the server to its actual behavior, and the player
becomes the controller of its server player!
If the player gets the current GPSinfo via its reflection, the server should
immediately 4 invoke getGPSin fo() via the ROClient (pass through). The

4 Almost immediately, depending on the network latency.